Multi-point locking systems for casement windows have been provided in the past to secure a window sash to a window frame at one or more locking points (e.g. a strike and mating receiver arrangement), typically located at two points (i.e. upper and lower) along the vertical edge of the sash and frame. Such locking systems are adapted to respond to the manipulation of an operator mechanism (typically with a rotatable handle) through which an input force is applied (the operator typically being located at the side of the window frame adjacent to or between the locking points) which actuates a locking mechanism (including a lockbar and a lockbar retainer) to engage the locking points. Such locking systems may engage either all of the locking points at the same time according to a common arrangement, or each locking point sequentially, as shown in U.S. Pat. No. 4,991,886, issued to Nolte et al. and U.S. Pat. No. 5,118,145, issued to Tucker.
When simultaneous engagement of all locking points is attempted, considerable input force may be required to manipulate the handle, particularly if there is any misalignment between the sash and the frame or of the corresponding elements of one or more locking points (e.g. strikes and receivers). In addition, there is a possibility that due to misalignment (or other effects) less than all of the locking points will actually engage, which results in the incomplete "locking" of the window.
As disclosed in the Nolte patent, it has been found that the effects of misalignment may be reduced in an arrangement providing for sequential engagement of the locking points (e.g. strikes and keepers). However, in the sequential locking arrangement of the Nolte patent, which includes a set of keepers with a ramped section and generally planar section, with mating strikes mounted at varied centers (i.e. distances relative to the corresponding mating keeper), the input force required for locking may be discontinuous. Depending upon the alignment of the window or arrangement of the various locking points, greater input force may be necessary for engagement of one locking point than another.
It would be advantageous to provide a progressive multi-point locking system for a casement window offering advantages over both a conventional locking system (i.e. where all of the locking points are simultaneously engaged) and a sequential locking system (i.e. where the locking points are engaged in sequence). It would be advantageous to have a progressive locking system that readily provides for smooth and even locking action. It would also be advantageous to have a window locking system adapted for mounting of the operator mechanism (with handle) at the bottom of the frame and mounting of the locking mechanism (with locking points) at the side, including a motion translation device of relatively simple construction coupling the operator mechanism to the locking mechanism. It would further be advantageous to have an arrangement wherein it is readily possible to remove the handle and a bezel of the operator mechanism (which is secured to the frame by fasteners which are accessible from inside whether the window is in the locked or the unlocked position) to allow for repair without damaging the window or the frame.